The circuit densities in modern integrated circuit devices require that the heat generated during operation of such devices be efficiently removed in order to maintain desirable operating temperatures (e.g., less than 85.degree. C.) to maximize processing speed and reliability, and prevent destruction of such devices by overheating. A typical microprocessor may comprise over 1 million transistors, operating at 50 megahertz, and the trend in the semiconductor industry today, is to make microprocessors smaller and more powerful (i.e., more transistors operating at a faster speed). As the heat generated by typical microprocessors increases, the difficulties encountered in providing compact, thermally-efficient, and reliable cooling devices becomes more critical.
A common approach to supplemental cooling has been to attach heat sinks with cooling fins to integrated circuit devices. Typical heat sinks for attachment to integrated circuits are illustrated in U.S. Pat. Nos. 4,541,004, 4,546,405, 4,611,238, 4,620,216 and 4,682,651. Other supplemental cooling devices include fans mounted on the heat sinks to increase cooling capacity. In one such device, the fan is mounted on top of the heat sink and is attached to the heat sink by threaded fasteners. The heat sink includes four plastic tabs, and each tab depends downward from a respective corner of the heat sink. When the heat sink is mounted on the casing of an electronic device, each of the four tabs is snapped into a respective recess formed in the casing in order to lock the heat sink and fan assembly to the casing. In order to unlock the heat sink and fan assembly from the casing, a tool is necessary to release the tabs from the corresponding recesses. Similarly, in order to remove the fan from the heat sink, the threaded fasteners must be removed by a screwdriver.
Thermoelectric cooling devices, such as the "ICECAP" module manufactured by Velox Computer Technology, Inc. of Sanka Clara, Calif., have also been developed to increase cooling capacity. The Velox device comprises a Peltier-effect thermoelectric cooler, including a "cold" plate attached to the microprocessor, a "hot" plate attached to a heat sink, and two semiconductors having dissimilar electrical properties (n-type and p-type semiconductors) mounted between the hot and cold plates. When a voltage is applied to the cooler, the hot plate side becomes relatively warm and the cold plate side becomes relatively cool (the Peltier effect), thus transferring the heat generated by the microprocessor from the cold plate to the hot plate, and in turn to the heat sink. An optional fan is mounted in a fixed fashion by threaded fasteners to the heat sink, which blows air through the cooling fins of the heat sink, dissipating the heat within the module.
Although the thermoelectric cooler has a higher cooling capacity than a typical heat sink, it is relatively expensive. Also, these types of supplemental cooling devices with integral fans can become a limiting factor in the reliability of associated integrated circuit devices. Typically, the expected operational life of a fan is less than that of a microprocessor. However, with a modern, more powerful microprocessor, if the supplemental cooling fan fails, continued operation of the microprocessor will frequently cause it to overheat and destroy itself, possibly within a matter of minutes. Because known supplemental cooling fans are fixedly attached to the microprocessors and/or to the heat sinks attached to the microprocessors, when such a cooling fan fails, typically the associated microprocessor must be discarded.